Re: [PATCH] gpio: pca953x: Fix warning when HW interrupts are rescheduled by the softirq tasklet

[Christian Gmeiner <christian.gmeiner@xxxxxxxxx>]

Hi all

2014-09-26 11:07 GMT+02:00 Linus Walleij <linus.walleij@xxxxxxxxxx>:
> On Thu, Sep 25, 2014 at 6:26 PM, Grygorii Strashko
> <grygorii.strashko@xxxxxx> wrote:
>> On 09/25/2014 11:07 AM, Linus Walleij wrote:
>>> On Wed, Sep 24, 2014 at 2:28 PM, Grygorii Strashko
>>> <grygorii.strashko@xxxxxx> wrote:
>>>> On 09/24/2014 02:17 PM, Linus Walleij wrote:
>>>
>>>>> So PCA cannot use gpiochip_set_chained_irqchip()?
>>>>
>>>> Yes. It can't - pca is i2c device.
>>>
>>> ? I don't get this statement.
>>>
>>> Why does the fact that it is an I2C device matter?
>>> We have several devices that are in fact on top of
>>> I2C (albeit as MFD cells) like gpio-tc3589x.c.
>>
>> gpio-tc3589x.c doesn't call gpiochip_set_chained_irqchip()
>
> Ah yeah you're right of course. I considered adding a separate
> registration function for the sleeping handlers, like
> gpiochip_set_threaded_irqchip() that would handle
> setting up the nested case.
>
>>> Yes, but the .map function isn't called until a client
>>> wants to use an IRQ. And that won't happen until after
>>> we exit the whole .probe() function.
>>
>> .map function is called from irq_create_mapping() which,
>> in turn, can be called as from irq_domain_add_simple() -
>> as result .map will be always called from gpiochip_irqchip_add().
>
> Ah yeah you're right, I was just wrong here :-/
>
>>> Well it happens in one single driver, and was done by me.
>>> Maybe I should either disallow that, as that means we're adding
>>> multiple parents (which is what you want, right?) or actually
>>> implement it in a way so that multiple parents can be handled
>>> by the helpers, by adding the parents to a list or something.
>>
>> Sorry, but It seems the simplest way is to allow drivers to manage
>> parent IRQs for the complex cases. So, I vote for custom .map()
>> callback, but It could be not too simple to implement it, because
>> private driver data need to be passed as parameter to this callback
>> somehow.
>
> Yeah. Well what I'm thinking as subsystem maintainer, is that
> when I added the generic GPIOlib irqchip helpers we managed to
> smoke out a large:ish set of subtle bugs that different drivers
> had created independently of each other.
>
> So centralizing code is very important if at all possible to bring
> down the maintainer burden.
>
> So for that reason I'm looking a second and a third time at these
> things before going ahead with custom code in drivers...
>
>> === Simple one - driver need to set parent_irq before adding gpiochip ===
>>
>> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
>> index 8aa84d5..292840b 100644
>> --- a/drivers/gpio/gpiolib.c
>> +++ b/drivers/gpio/gpiolib.c
>> @@ -447,8 +447,11 @@ static int gpiochip_irq_map(struct irq_domain *d, unsigned int irq,
>>         irq_set_lockdep_class(irq, &gpiochip_irq_lock_class);
>>         irq_set_chip_and_handler(irq, chip->irqchip, chip->irq_handler);
>>         /* Chips that can sleep need nested thread handlers */
>> -       if (chip->can_sleep)
>> +       if (chip->can_sleep) {
>>                 irq_set_nested_thread(irq, 1);
>> +               if (chip->parent_irq)
>> +                       irq_set_parent(irq, chip->parent_irq);
>> +       }
>
> Yeah I need to think of something like this...
>

I did run into exact the same situation with a 4.1.1 kernel :)

[  312.863047] ------------[ cut here ]------------
[  312.867681] WARNING: CPU: 1 PID: 12 at kernel/irq/manage.c:696
irq_nested_primary_handler+0x30/0x38()
[  312.876901] Primary handler called for nested irq 301
[  312.881953] Modules linked in: uinput ipv6 smsc95xx usbnet mii
imx2_wdt etnaviv(C) matrix_keypad matrix_keymap ar1021_i2c
[  312.893067] CPU: 1 PID: 12 Comm: ksoftirqd/1 Tainted: G        WC
   4.1.1 #9
[  312.900378] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
[  312.906906] Backtrace:
[  312.909377] [<c0013298>] (dump_backtrace) from [<c0013488>]
(show_stack+0x20/0x24)
[  312.916947]  r6:00000009 r5:ffffffff r4:00000000 r3:dc8ba301
[  312.922673] [<c0013468>] (show_stack) from [<c05743c4>]
(dump_stack+0x70/0xc0)
[  312.929924] [<c0574354>] (dump_stack) from [<c002b7b8>]
(warn_slowpath_common+0x88/0xc0)
[  312.938029]  r5:000002b8 r4:00000000
[  312.941678] [<c002b730>] (warn_slowpath_common) from [<c002b8ac>]
(warn_slowpath_fmt+0x40/0x48)
[  312.950391]  r8:00000000 r7:c07b1314 r6:0000012d r5:eea07720 r4:c3048840
[  312.957233] [<c002b870>] (warn_slowpath_fmt) from [<c0075798>]
(irq_nested_primary_handler+0x30/0x38)
[  312.966467]  r3:0000012d r2:c06b9128
[  312.970113] [<c0075768>] (irq_nested_primary_handler) from
[<c0075200>] (handle_irq_event_percpu+0x70/0x2d0)
[  312.979967] [<c0075190>] (handle_irq_event_percpu) from
[<c00754ac>] (handle_irq_event+0x4c/0x6c)
[  312.988854]  r10:00000002 r9:00000018 r8:00000000 r7:c07b1314
r6:c3048840 r5:eea07720
[  312.996812]  r4:eea076c0
[  312.999395] [<c0075460>] (handle_irq_event) from [<c0078204>]
(handle_simple_irq+0xa4/0xc8)
[  313.007760]  r6:c07c5404 r5:eea07720 r4:eea076c0 r3:00000003
[  313.013536] [<c0078160>] (handle_simple_irq) from [<c0077cd4>]
(resend_irqs+0x50/0x7c)
[  313.021468]  r5:c07c5404 r4:0000012d
[  313.025119] [<c0077c84>] (resend_irqs) from [<c002f99c>]
(tasklet_action+0x94/0x140)
[  313.032877]  r6:00000000 r5:c07c5444 r4:c07c5440 r3:c0077c84
[  313.038655] [<c002f908>] (tasklet_action) from [<c002eea8>]
(__do_softirq+0xa0/0x3c8)
[  313.046500]  r8:c07c1908 r7:00000006 r6:00000001 r5:00000040
r4:c07ba098 r3:c002f908
[  313.054387] [<c002ee08>] (__do_softirq) from [<c002f208>]
(run_ksoftirqd+0x38/0x54)
[  313.062058]  r10:00000002 r9:00000000 r8:c07c1908 r7:00000000
r6:00000001 r5:00000001
[  313.070017]  r4:ee893980
[  313.072605] [<c002f1d0>] (run_ksoftirqd) from [<c004b1e4>]
(smpboot_thread_fn+0x1f8/0x2f0)
[  313.080906] [<c004afec>] (smpboot_thread_fn) from [<c0047744>]
(kthread+0xe8/0x104)
[  313.088578]  r10:00000000 r8:00000000 r7:c004afec r6:ee893980
r5:00000000 r4:ee893a40
[  313.096558] [<c004765c>] (kthread) from [<c000fac8>]
(ret_from_fork+0x14/0x2c)
[  313.103796]  r7:00000000 r6:00000000 r5:c004765c r4:ee893a40
[  313.109560] ---[ end trace 96052cda48865769 ]---


Linus, what is the state of the your last thinking about this topic?

greets
--
Christian Gmeiner, MSc

https://soundcloud.com/christian-gmeiner
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